Insects such as flies and mosquitoes pose great hazards to the living quality of human beings, but insecticides, which are the most direct solution to such hazards, are harmful to the human body and environment. Hence, a wide variety of insect resistive products based on the susceptibility of insects to scents, humidity and light are always developed, including, for example, fly catching paper and mosquito killer lamps. Light has enormous ecological effects on insects. Taking fireflies for example, the flashing frequency of their abdominal bioluminescence is depended upon as means for attracting mates and communication in the dark. Many insects can sense much higher flashing frequency than human eyes, and some kind of swing pattern in flashing frequency can make insects nervous and uncomfortable.
Light emitting diode (LED) is a device that emits light when electrically biased in the forward direction of a semiconductor p-n junction, and is characterized by heterogeneous dual junction and quantum wells. The first commercial red GaAsP LED was offered by General Electric Company in 1962. The luminous flux of the first red LED was 0.11 m/W, or 1/150 times of an ordinary lamp, with an emissive efficiency increasing by one order of magnitude per decade approximately. The recent advent of high power white LEDs in the wake of implementation of blue LEDs and green LEDs heralds gradual transition from decoration to illumination in terms of the purpose of LEDs, paving the way for ultimate replacement of conventional light bulbs by LEDs. In addition to being environmentally friendly and power saving, LED can be turned on and off in high frequency up to over MHz range. Furthermore, there have been plenty of methods for pulse width modulation (PWM) dimming in LED lighting.